Modern operations for the exploration and production of oil and gas rely on access to a variety of information regarding subsurface geological parameters and conditions. Such information typically includes characteristics of Earth formations traversed by a borehole, as well as data relating to the size and mud of the borehole itself. The collection of information relating to subsurface conditions, which is commonly referred to as “logging,” can be performed by several methods, including wireline logging and logging while drilling (LWD).
In wireline logging, a sonde is lowered into the borehole after some or all of the well has been drilled. The sonde hangs at the end of a wireline cable that provides mechanical support to the sonde and also provides an electrical connection between the sonde and electrical equipment located at the surface. In accordance with existing logging techniques, various parameters of the Earth's formations are measured and correlated with the position of the sonde in the borehole as the sonde is pulled uphole. In LWD, a drilling assembly includes sensing instruments that measure various parameters as the formation is penetrated, thereby enabling measurement of the formation during the drilling operation. Among the available wireline and LWD tools are a variety of resistivity logging tools including devices configured for taking MCI measurements.